Electronic sensors are employed in a number of different fields of technology. Such sensors may be employed to detect changes in environmental parameters, such as atmospheric pressure, or may be employed to detect changes in forces applied to the object to which they are attached, for example.
One type of sensor that is often utilized in sensor applications is the “flow sensor”. An example of a flow sensor is disclosed in U.S. Pat. No. 6,871,537, entitled “Liquid Flow Sensor Thermal Interface Methods and Systems”, which issue to Richard W. Gehman, et al. on Mar. 29, 2005 and is assigned to Honeywell International Inc. of Morristown, N.J., U.S.A. U.S. Pat. No. 6,871,537, which is incorporated herein by reference that measures the thermal conductivity of a fluid. The sensor disclosed in U.S. Pat. No. 6,871,537 is configured to comprise one or more sensing element associated with a sensor substrate. A heater is generally associated with said sensor wherein said heater provides heat to said fluid. A film component is also provided that isolates said fluid from said heater and said sensor, such that said film component conducts heat in a direction from said heater to said sensor, thereby forming a thermal coupling between said sensor, said heater and said fluid, which permits said sensor to determine a composition of said fluid by measuring thermal conductivity thereof without undesired losses of heat in other directions. The film component can be configured on or in the shape of a tubing or a flow channel.
Other types of sensors include “temperature sensors” and “pressure sensors”. An example a pressure and/or temperature sensor is disclosed in U.S. Pat. No. 6,907,787, entitled “Surface Acoustic Wave Pressure Sensor with Microstructure Sensing Elements,” which issued to James Cook, et al. on Jun. 21, 2005 and is assigned to Honeywell International Inc. of Morristown, N.J., U.S.A. U.S. Pat. No. 6,907,787, which is incorporated herein by reference in its entirety, generally discloses a pressure and temperature sensor system, comprising one or more microstructure temperature-sensing elements formed on a substrate within a hermetically sealed area thereof, wherein such microstructure temperature-sensing elements comprise (Surface Acoustic Wave) SAW temperature-sensing elements. Additionally, one or more microstructure pressure-sensing elements can be located above a sensor diaphragm on the substrate, such that the microstructure pressure-sensing element is formed from a SAW pressure-sensing element. One or more contacts can also be provided, which assist in maintaining the hermetically sealed area and which protrude through the substrate for support and electrical interconnection of the pressure and temperature sensor system.
For satisfactory functioning of a sensor, regardless of the type of sensor utilized, prior calibration of the sensor system or the individual sensors is preferably accomplished in principle for the subsequent accurate measurement of environmental parameters. Calibration can be accomplished in a laboratory-like environment either before or after deployment of the sensors. The various calibration methods usually require controlled movement of the sensors or the objects or environmental conditions detected by the sensor systems. Often it is even desirable to detect a particular parameter, which is then referred to as a calibration field accordingly. To guarantee permanent functional reliability, subsequent repeated checking of the calibration for possible changes is desirable, which may be very complicated.
Sensors of extremely low-cost are typically based on sophisticated but extremely compact components and require new methods of calibration. Traditional sensors are calibrated by laser-trimming of resistors, capacitors, inductors and/or other necessary sensor components. Trimming in this manner, however, increases the overall cost of sensor, and in some cases, may introduce drift due to the heat from laser. RFID provides another technique for calibration and data storage, but in extremely low cost sensor designs, even, for example, 5-10 cents RFID components contribute a great deal to the overall sensor costs.
In manufacturing processes for sensor devices, particularly those, which incorporate substrate and die processing, numerous expensive and time-consuming steps are involved in producing such sensor device assemblies. These steps may include the following: (1) forming a dice on a sensor substrate, (2) testing the dice, (3) cutting dice from the substrate, (4) connecting a die or dice to a lead frame, (5) encapsulating the die or dice, lead frame, connecting wires, and any auxiliary circuitry, (6) performing burn-in and/or providing other stresses to the dice, and (7) testing the sensor device assembly at various stages of processing.
In sensor manufacturing, typically, the term “front-end” refers to the fabrication of sensor devices to the level of completed and tested components. The term “backend” refers to production stages of sensor devices occurring after the front-end and including such sensor device production stages as packaging, burn-in, testing, sorting, marking, and environmental testing.
When tested, a sensor device may have some failure due to various causes including, but not limited to, an internal defect in the die or chip, a bad bonding connection, or a bad connection between a lead finger and a probe or other test device. Failures in a completed sensor device assembly can prevent it from operating as intended. In spite of painstaking attention to detail, failures may be introduced at various levels of production. For example, defects in forming the die or substrate may cause a failure. It has been found, however, that some defects are manifest immediately, while other defects are manifest only after the die has been operated for some period of time.
It is therefore believed that a need exists for reducing sensor production costs by implementing improved calibration methodologies and systems, and also providing for improved sensor manufacturing and binning processes. Such improvements are therefore disclosed herein.